Testing the measurement invariance of the University of Washington Self-Efficacy Scale short form across four diagnostic subgroups

Abstract

Purpose

The University of Washington Self-Efficacy Scale (UW-SES) was originally developed for people with multiple sclerosis (MS) and spinal cord injury (SCI). This study evaluates the measurement invariance of the 6-item short form of the UW-SES across four disability subgroups. Evidence of measurement invariance would extend the UW-SES for use in two additional diagnostic groups: muscular dystrophy (MD) and post-polio syndrome (PPS).

Methods

Multi-group confirmatory factor analysis was used to evaluate successive levels of measurement invariance of the 6-item short form, the UW-SES: (a) configural invariance, i.e., equivalent item-factor structures between groups; (b) metric invariance, i.e., equivalent unstandardized factor loadings between groups; and (c) scalar invariance, i.e., equivalent item intercepts between groups. Responses from the four groups with different diagnostic disorders were compared: MD (n = 172), MS (n = 868), PPS (n = 225), and SCI (n = 242).

Results

The results of this study support that the most rigorous form of invariance (i.e., scalar) holds for the 6-item short form of the UW-SES across the four diagnostic subgroups.

Conclusions

The current study suggests that the 6-item short form of the UW-SES has the same meaning across the four diagnostic subgroups. Thus, the 6-item short form is validated for people with MD, MS, PPS, and SCI.

Appendices

Appendix 1

University of Washington Self-Efficacy Scale 6-item short form

How confident are you that	Not at all	A little	Quite a bit	A lot	Completely
1. You can keep the physical discomfort related to your health condition or disability from interfering with the things you want to do?	□	□	□	□	□
2. You can keep your health condition or disability from interfering with your ability to deal with unexpected events?	□	□	□	□	□
3. You can keep your health condition or disability from interfering with your ability to interact socially?	□	□	□	□	□
4. You can keep your health condition or disability from being the center of your life?	□	□	□	□	□
5. You can bounce back from frustration, discouragement or disappointment that your health condition or disability may cause you?	□	□	□	□	□
6. You can figure out effective solutions to issues that come up related to your health condition or disability?	□	□	□	□	□

1. Items can be summed and then transformed to generate a total score for each form. Responses to items are made on a five-point scale: 1 = not at all, 2 = a little, 3 = quite a bit, 4 = a lot, 5 = completely

Appendix 2

6-Item short form summary score to T-score concordance table

Summary	Theta score	T-score
6	−3.00	20.0
7	−2.62	23.8
8	−2.35	26.5
9	−2.11	28.9
10	−1.90	31.0
11	−1.71	32.9
12	−1.53	34.7
13	−1.36	36.4
14	−1.20	38.0
15	−1.04	39.6
16	−.89	41.1
17	−.74	42.6
18	−.59	44.1
19	−.44	45.6
20	−.29	47.1
21	−.14	48.6
22	.02	50.2
23	.18	51.8
24	.34	53.4
25	.51	55.1
26	.69	56.9
27	.90	59.0
28	1.13	61.3
29	1.41	64.1
30	1.89	68.9

1. All 6 items are summed as a first step. After summing, scores are transformed to a T-score metric using the concordance table provided above. For comparison purposes, the mean in the development sample was 49.9 with a SD of 9.3